Thinning out brass tube walls?

[jrista]

Since mid summer, I've delved into higher end pen kits, fountain pens and roller balls. I also started working with a variety of these faux stone blanks. I've had some problems, especially with these Triton kits that people seem to want (I have some cambridge as well that most people seem to find too large). The blanks crack when compressing the pen parts into the tubes...especially with the Triton where there is a long black plastic threaded insert that needs to go rather far into the cap tube.

I received some recommendations a while back to thin out the tube walls to the point where the pen parts are just about a slip fit, and glue them in place. I've got another pen to make today, for a friend as a gift to his wife. So I need to make sure that there is no cracking with this one. It is another Triton kit, and it is another one of these marbled gold blanks, which was the first one I had problems with about a month back. I'm wondering how best to thin out the walls of the tube. I have some small files that might do the trick, but it seems like a lot of imprecise manual work, especially for the cap, and I am wondering if anyone has any other more efficient and precise options. I thought about drilling...but I am worried that would really just shred the tube, rather than actually thin the walls.

 

[carlmorrell]

I know the upper cap with the long plastic inserts make me nervous, and I have made many. What I do is after I turn the blank, I use a round file. My favorite is one for my chain sw. It's probably 1.4" diameter and a foot long with a handle. I file the crap out of the inside. I never get it to the point where the insert slips in, but I make sure the entire inside is nice and shiny. Interested to know if there is a better way.

 

[qquake]

Why not a Dremel with a grinding stone?

453 Sharpening Bits | Dremel

Dremel 453 5/32 In. (4.0 mm) Chainsaw Sharpening Grinding Stone

us.dremel.com

 

[Fred Bruche]

I typically use a combination of coarse sanding paper and a Morakniv carving knife. I feel I have more control than using a round file and I work only on the area that will be in contact with the hardware.

 

[wrjones224]

I also use a Dremel but with an engraving bit. Run it around the brass tube a few times and that typically does the trick. Less hand work and much faster.

 

[Curly]

The best way is with an adjustable reamer. You can creep up on the size until it is perfect. Something to consider if doing this a lot. By the way the reamers are turned in one direction by hand and not in a drill etc. https://www.grizzly.com/products/grizzly-7-pc-adjustable-reamer-set/h5938

What I do, because it is simple, is to take a dowel or rod and saw a slot in the end. Then cut a strip of sand paper or better cloth and wrap it from the slot around the dowel a few times so the end trails from the direction of rotation of your drill. Put the dowel and paper in the tube and spin your drill a little at a time to sand out the inside of the tube as much as you need. Note if you go too far you will be sanding your fingers.

I don't recommend qquake's question/suggestion. Grinding wheels and stones load up, get clogged, on non ferrous metals like brass and aluminium. On a big stone like in a bench grinder they can heat up and explode. A small point in the Dremel just wrecks them. Sanding cartridges would be better.

 

[wouldentu2?]

I know this will not work with all pens, but you might be able to pre-stretch the tube by pressing it together and then tapping it out before gluing up the blank.

 

[eteska]

I have used the same method as Curly. A wooden dowel with a slit cut in one end. Chuck it in a cordless drill and go at it until they slide in with little or no resistance.

 

[Monty]

I second Curly's suggestion for using an adjustable reamer. This set from Amazon works well for me.

 

[Curly]

Monty that is a heck of a deal and perfect for the light duty work we would put them to.

 

[qquake]

I don't know how big the tube is, but Dremel has a smaller diameter sanding drum.

430 Sanding Bits | Dremel

Dremel 430 1/4 In. (6.4 mm) 60 Grit Sanding Band

us.dremel.com

You could also try a carving bit.

Dremel 115 Carving Bit - dremel.com

 

[jrista]

The best way is with an adjustable reamer. You can creep up on the size until it is perfect. Something to consider if doing this a lot. By the way the reamers are turned in one direction by hand and not in a drill etc. https://www.grizzly.com/products/grizzly-7-pc-adjustable-reamer-set/h5938

What I do, because it is simple, is to take a dowel or rod and saw a slot in the end. Then cut a strip of sand paper or better cloth and wrap it from the slot around the dowel a few times so the end trails from the direction of rotation of your drill. Put the dowel and paper in the tube and spin your drill a little at a time to sand out the inside of the tube as much as you need. Note if you go too far you will be sanding your fingers.

I don't recommend qquake's question/suggestion. Grinding wheels and stones load up, get clogged, on non ferrous metals like brass and aluminium. On a big stone like in a bench grinder they can heat up and explode. A small point in the Dremel just wrecks them. Sanding cartridges would be better.

Thanks for the details, I appreciate it! I had not considered an adjustable reamer...that may be the best tool for the job.

I do have some Dremel bits, and sanding drums. The bits are small enough to get into the tube...not sure about the sanding drums. One of my concerns about the drums was if they weren't inserted at just the right angle, they could bind up, and that would probably destroy the tube and the blank.

I don't know how big the tube is, but Dremel has a smaller diameter sanding drum.

430 Sanding Bits | Dremel

Dremel 430 1/4 In. (6.4 mm) 60 Grit Sanding Band

us.dremel.com

You could also try a carving bit.

Dremel 115 Carving Bit - dremel.com

I may have to try some of those 430 sanding drums. The ones I have are almost the size of the tubes...these are standard fountain pens (and rollerballs, too, actually), so most are 10.5mm/12.5mm tubes. I do have some Cambridge kits, which are 31/64ths and 33/64ths (waiting on a bit for the latter to arrive...thought I had it, but my bradpoint imperial set stopped at 1/2"), and those use really large tubes. I could probably use just about anything to sand or grind those down.

Until the adjustable reamers arrive, I'll try the dremel bits, and see how it goes. I am not sure if I'll try the drums...just too worried they will bind up inside the tube due to a slight angle and ruin it.

 

[Roly]

I have had a fair bit of success with a chain saw file, fine cut and long reach with parallel sides. It is a bit time consuming and I started using it initially to remove some glue that had stuck on the inside, havn't had a failure since.

 

[randyrls]

Rather than removing any brass from the tube, I insert a transfer punch (TF) just smaller into the tube before glue up. Twist the TF around until the metal fitting is a slip fit. Now glue into the blank with Gorilla Glue to add some resilience to the blank. It may be necessary to use a slightly larger drill bit on the blank. After turning blank, put a small drop of medium or thick CA INSIDE the tube. Insert fitting with a twisting motion and let cure. Don't assemble until the CA is completely cured (blushing).

 

[WriteON]

I went the other direction as the blank was tubed, trimmed, ready to go. I use a stone on a Dremel and skimmed the kit so it inserted into loosely into the tube..... then glued. Yes it heats up and warms up my fingers but I work it out.

 

[jrista]

I went the other direction as the blank was tubed, trimmed, ready to go. I use a stone on a Dremel and skimmed the kit so it inserted into loosely into the tube..... then glued. Yes it heats up and warms up my fingers but I work it out.

Hmm...how did you hold the kit parts? By hand, or did you have some kind of vice or something?

 

[WriteON]

Hand.

Hmm...how did you hold the kit parts? By hand, or did you have some kind of vice or something?

By hand. Just be careful. Definitely wear eye protection. Improvise somehow with a rubber grip if that will help.

 

[jttheclockman]

Thanks for the details, I appreciate it! I had not considered an adjustable reamer...that may be the best tool for the job.

I do have some Dremel bits, and sanding drums. The bits are small enough to get into the tube...not sure about the sanding drums. One of my concerns about the drums was if they weren't inserted at just the right angle, they could bind up, and that would probably destroy the tube and the blank.



I may have to try some of those 430 sanding drums. The ones I have are almost the size of the tubes...these are standard fountain pens (and rollerballs, too, actually), so most are 10.5mm/12.5mm tubes. I do have some Cambridge kits, which are 31/64ths and 33/64ths (waiting on a bit for the latter to arrive...thought I had it, but my bradpoint imperial set stopped at 1/2"), and those use really large tubes. I could probably use just about anything to sand or grind those down.

Until the adjustable reamers arrive, I'll try the dremel bits, and see how it goes. I am not sure if I'll try the drums...just too worried they will bind up inside the tube due to a slight angle and ruin it.

Do not over think this. A round rats tail file works great. That is what I use all the time. Sandpaper would be the next choice because you can sneak up on it. I use red locktite to adhere parts in. Do not drill out. Reamers are an added expense but I guess they can work. Never used them. Good luck.

 

[duncsuss]

I second Curly's suggestion for using an adjustable reamer. This set from Amazon works well for me.

Thanks for this link - order placed